Salicin is a naturally occurring compound found in the bark of several species of trees, primarily North American in origin, that are from the willow, poplar, and aspen families. White willow, from whose Latin name, Salix alba, the term salicin is derived, is the most well known source of this compound, but it is found in a number of other trees, shrubs, and herbaceous plants as well being synthesized commercially. It is a member of the glucoside family of chemicals and is used as an analgesic and antipyretic. Salicin is used as a precursor for the synthesis of salicylic acid and acetylsalicylic acid, commonly known as aspirin.
A colorless, crystalline solid in its pure form, salicin has the chemical formula C13H18O7. Part of its chemical structure is equivalent to the sugar glucose, meaning it is classified as a glucoside. It is soluble, but not strongly so, in water and alcolhol. Salicin has a bitter taste and is a natural analgesic and antipyretic, or fever reducer. In large quantities, it can be toxic, and overdoses may lead to liver and kidney damage. In its raw form, it may be mildly irritating to skin, respiratory organs, and eyes.
For centuries, salicin has been used to relieve minor aches and pains, especially those caused by inflammation, to help reduce minor fevers, and as a gastric stimulant. It was long known that white willow bark extract possessed such qualities, but it was not known until the 19th century that salicin was the active compound that produced these effects. Today, processed white willow bark extract is normalized for a consistent content, usually 8% by weight. Willow bark extracts are available in stores that sell herbal remedies and is not usually found in more mainstream shops like supermarkets and pharmacies. It is preferred, however, by some people over aspirin.
Salicin was used to first produce the drug aspirin, with which it shares many similarities. Both substances, when metabolized in the human body, are partly reduced to salicylic acid. Salicylic acid was studied and found to be an inferior alternative to salicin. Aspirin was developed in an effort to create a similar but more effective compound. Salicin acts in a very similar way to aspirin but does not possess the unwanted side effects that are sometimes associated with aspirin, including gastric upset and a poorly understood but well documented connection with Reye's syndrome, a dangerous and potentially fatal disease that usually occurs in children.